 /*
  * $Header: /cvshome/build/org.osgi.service.wireadmin/src/org/osgi/service/wireadmin/Consumer.java,v 1.10 2006/07/11 00:54:10 hargrave Exp $
  *
  * Copyright (c) OSGi Alliance (2002, 2006). All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 package org.osgi.service.wireadmin;

 /**
  * Data Consumer, a service that can receive udpated values from
  * {@link Producer} services.
  *
  * <p>
  * Service objects registered under the <code>Consumer</code> interface are
  * expected to consume values from a Producer service via a <code>Wire</code>
  * object. A Consumer service may poll the Producer service by calling the
  * {@link Wire#poll} method. The Consumer service will also receive an updated
  * value when called at it's {@link #updated} method. The Producer service
  * should have coerced the value to be an instance of one of the types specified
  * by the {@link Wire#getFlavors} method, or one of their subclasses.
  *
  * <p>
  * Consumer service objects must register with a <code>service.pid</code> and a
  * {@link WireConstants#WIREADMIN_CONSUMER_FLAVORS} property. It is recommended
  * that Consumer service objects also register with a
  * <code>service.description</code> property.
  *
  * <p>
  * If an <code>Exception</code> is thrown by any of the <code>Consumer</code>
  * methods, a <code>WireAdminEvent</code> of type
  * {@link WireAdminEvent#CONSUMER_EXCEPTION} is broadcast by the Wire Admin
  * service.
  *
  * <p>
  * Security Considerations - Data consuming bundles will require
  * <code>ServicePermission[Consumer,REGISTER]</code>. In general, only the Wire
  * Admin service bundle should have this permission. Thus only the Wire Admin
  * service may directly call a Consumer service. Care must be taken in the
  * sharing of <code>Wire</code> objects with other bundles.
  * <p>
  * Consumer services must be registered with their scope when they can receive
  * different types of objects from the Producer service. The Consumer service
  * should have <code>WirePermission</code> for each of these scope names.
  *
  * @version $Revision: 1.10 $
  */
 public interface Consumer {
     /**
      * Update the value. This Consumer service is called by the <code>Wire</code>
      * object with an updated value from the Producer service.
      *
      * <p>
      * Note: This method may be called by a <code>Wire</code> object prior to this
      * object being notified that it is connected to that <code>Wire</code> object
      * (via the {@link #producersConnected} method).
      * <p>
      * When the Consumer service can receive <code>Envelope</code> objects, it
      * must have registered all scope names together with the service object,
      * and each of those names must be permitted by the bundle's
      * <code>WirePermission</code>. If an <code>Envelope</code> object is delivered
      * with the <code>updated</code> method, then the Consumer service should
      * assume that the security check has been performed.
      *
      * @param wire The <code>Wire</code> object which is delivering the updated
      * value.
      * @param value The updated value. The value should be an instance of one of
      * the types specified by the {@link Wire#getFlavors} method.
      */
     public void updated(Wire wire, Object value);

     /**
      * Update the list of <code>Wire</code> objects to which this Consumer service
      * is connected.
      *
      * <p>
      * This method is called when the Consumer service is first registered and
      * subsequently whenever a <code>Wire</code> associated with this Consumer
      * service becomes connected, is modified or becomes disconnected.
      *
      * <p>
      * The Wire Admin service must call this method asynchronously. This implies
      * that implementors of Consumer can be assured that the callback will not
      * take place during registration when they execute the registration in a
      * synchronized method.
      *
      * @param wires An array of the current and complete list of <code>Wire</code>
      * objects to which this Consumer service is connected. May be
      * <code>null</code> if the Consumer service is not currently connected
      * to any <code>Wire</code> objects.
      */
     public void producersConnected(Wire[] wires);
 }

